1. Field of the Invention
This invention relates generally to the field of oxygen generation, storage, and delivery, and, in particular, to systems and methods to efficiently and effectively transfill oxygen into portable oxygen delivery devices.
2. Description of the Related Art
More and more people are using oxygen therapy outside the hospital, permitting them to lead active, productive lives. People with asthma, emphysema, chronic bronchitis, occupational lung disease, lung cancer, cystic fibrosis, congestive heart failure, or other respiratory disorders may use oxygen therapy at home and use portable oxygen therapy devices outside of the home. Recent developments in oxygen therapy technology have given those dependent upon oxygen a variety of in-home and portable options for oxygen therapy. There are three main ways to personally administer oxygen therapy outside of a medical facility, (1) oxygen concentrators, (2) liquid oxygen devices, and (3) compressed gas devices. Each of these three types of solutions provide particular benefits and detriments.
First, oxygen concentrators, typically in the form of a pressure swing adsorption systems, are an excellent source of oxygen therapy for in home use. Pressure swing adsorption (“PSA”) systems are advantageous in that they can process ambient air, containing approximately 21% oxygen, and separate that oxygen from the ambient air. Thereby, the user can be supplied with higher concentrations of oxygen. While suitable for their intended purpose, oxygen concentrators are generally bulky and require access to a power source, such as an electrical outlet. Thus, oxygen concentrators are ill-suited for portability and are not intended for use with an ambulatory individual.
Second, a liquid oxygen (“LOX”) system can provide a convenient method of portable oxygen therapy. Liquid oxygen is advantageous because it occupies significantly less space than compressed gaseous oxygen. A conventional LOX system includes a large stationary LOX storage canister that stays in the home. The conventional system also includes a small, portable delivery apparatus that can be filled from the stationary unit for trips outside the home. Many first generation prior art systems have limited utilization due to the low LOX capacity of the portable delivery apparatus and the administered LOX flow rate. To maintain a liquid state, oxygen must be kept at a relatively cool temperature, e.g., around 300 degrees Fahrenheit below zero (−300° F.). Therefore, the liquid oxygen stored in LOX systems will evaporate, even if not used by the user. In this manner, the LOX system has a relatively short use period that expires regardless of whether the user is actually using the oxygen.
Third, compressed oxygen systems are generally prescribed for a variety of different types of oxygen therapy patients, including those that are relatively mobile and/or those for whom oxygen is not needed all the time, such as only when walking or performing physical activity. Small tanks containing compressed oxygen are well suited for portability in that they can be relatively light weight and they can maintain their supply of oxygen when not in use. Small portable compressed oxygen devices are limited, however, in how long they will last depending on the prescribed flow rate, the size (volume) of the tank and the pressure rating of the tank. Therefore, portable compressed oxygen devices must be refilled often.
Many prior art systems attempt to address the drawbacks presented by particular home oxygen therapy devices. For example, some oxygen concentrators have been designed to enable a user to fill portable compressed oxygen canisters from the oxygen concentrator. U.S. Pat. No. 5,853,062 (“the '062 patent”) describes a pressure swing adsorption system that is capable of providing oxygen enriched air a first pressure and a second pressure. As shown in FIG. 1 of the '062 patent, the PSA is enabled to receive ambient air and output oxygen enriched air at a first low pressure outlet 106 for use by a user. Typically, a user would connect a nasal cannula to first low pressure outlet 106 in a manner similar to the majority of PSA systems. Further the PSA system of the '062 patent provides a second output from the concentrator 104 to a pressure intensifier 109. Pressure intensifier 109 has a drive air cylinder and a first and second stage product gas cylinder. The drive air cylinder of pressure intensified 109 can be operated to compress the gaseous oxygen of concentrator 104 and connect to a high pressure outlet 112. Thereby, the user can connect and re-charge a cylinder with compressed gas.
U.S. Pat. No. 6,446,630 (“the '630 patent”) describes a PSA system configured to simultaneously provide oxygen therapy to a user and fill a portable oxygen cylinder. As shown in FIG. 1 of the '630 patent, the system provides an oxygen concentrator 11 connected to a flow position control valve 14 in communication with an inhalation sensor 21. When inhalation sensor 21 detects that the user is inhaling, the concentrator provides oxygen to the user. When the user is not inhaling, flow position control valve 14 connects the output of oxygen concentrator 11 to a compressor 17. Compressor 17 operates to compress the gas produced by oxygen concentrator 11 that is not used by the user. Once a sufficient quantity of gas is compressed, a portable gas cylinder 18 can be filled for use by the user.
U.S. Pat. No. 6,889,726 (“the '726 patent”) describes a device for filling portable high pressure cylinders with a compressor and an oxygen concentrator. As shown in FIG. 2 of the '726 patent, the system provides an oxygen concentrator 12 having a standard configuration of sieve beds 24 connected to a product tank 22 and flow rate restrictors 28. Thereby, oxygen concentrator 12 is operative to provide oxygen-enriched gas to a user device 14, such as a nasal cannula. Additionally, when the output of the concentrator 12 is greater than needed to supply user device 14, the excess enriched gas from the user device 14 is directed to compressor 60.
As shown in FIG. 1 of the '726 patent, compressor 60 compresses the oxygen-enriched gas flowing into it and outputs the gas to a coupling 70. When a portable tank is connected to coupling 70, the relatively high pressure gaseous oxygen output from compressor 60 flows through coupling 70 and into a portable tank 20. As disclosed in the '726 patent, filing portable tank 20 from compressor 60 takes about 1 to 12 hours. The '726 patent also discloses a reservoir 90 connected to compressor 60. Compressor 60 is enabled to fill reservoir 90 when a portable tank 20 is not connected to coupling 70. Once reservoir 90 has been filled, a portable tank 20 can be connected to coupling 70 and filled in a shorter time span than filling direct from compressor 60. As disclosed in the '726 patent, the initial fill time for reservoir 90 can be as much as a week.
While suitable for their intended purposes, conventional oxygen transfill systems suffer from many drawbacks. The most significant drawback is that these systems require a compressor. The use of a compressor presents many drawbacks for the user. Significantly, compressors require significant amounts of power to operate. For example, the compressor of the system disclosed in '726 patent must run constantly for an entire week to fill the reservoir of the system. Such extensive usage requires a tremendous amount of electrical power and can be costly to the user. Furthermore, compressors are often bulky and generate significant noise in operation and during power cycles. For example, the compressor for a prior art gaseous oxygen transfill system may routinely turn on and off dependent upon the user's oxygen demands, as the compressor only receives oxygen when there is an excess supply.
An additional drawback for the user of a compressor based gaseous oxygen transfill system is that compressor often requires periodic maintenance and repair. As relatively high demands are placed on the compressor for a prior gaseous oxygen transfill system, such as continually generating pressures in excess of 2000 psi, these compressors often fail. When the compressor fails, the entire gaseous oxygen transfill system becomes inoperable as the pressure of the gaseous oxygen coming from the concentrator is far below that required for a portable compressed oxygen device.
A further drawback of prior art gaseous oxygen transfill systems relates to the time period necessary to fill a portable gas container. For example, the gaseous oxygen transfill system of the '726 patent requires up to 12 hours to fill a portable tank from the compressor. As the pressure of the oxygen output from the concentrator is relatively low, a great deal of time is required to pressurize the gas to a level sufficient for portability.
On a commercial scale, portable compressed oxygen devices are most often filled with gaseous oxygen in an industrial process using a system of industrial scale devices. For example, commercial oxygen providers typically have a transfill system that involves the use of large capacity liquid oxygen dewars and pneumatic compressors. Conventional large capacity liquid oxygen dewars are typically bulky and extremely heavy devices that are stored in a commercial oxygen provider's warehouse. These conventional large capacity liquid oxygen dewars typically produce gaseous oxygen at relatively low pressures, around 100 to 300 pounds-force per square inch gauge (“psig”). The commercial oxygen provider typically retrieves gaseous oxygen from the large capacity liquid oxygen dewars and outputs it to a large scale pneumatic compressor enabled to pressurize the gaseous oxygen to a pressure sufficient for storage in a portable compressed oxygen device. Conventional large scale pneumatic compressors are typically very voluminous and loud devices that run on electrical power or even diesel engines.
After the pneumatic compressor has pressurized the gaseous oxygen, portable compressed oxygen devices can be filled with the pressurized gas. This method has many drawbacks and limitations. One of the most significant is that this industrial process is completely unavailable to the user of the oxygen therapy devices. Moreover, this industrial process must be performed by a skilled technician in an industrial environment with great precision to reduce the risk of injury. Furthermore, this process requires the commercial oxygen provider to retrieve portable compressed oxygen devices from the user's homes, take them back to the site of industrial system to be refilled, and then return the portable compressed oxygen devices to the homes of the users. This is costly, inefficient, and cumbersome for both the commercial oxygen provider and the user.
U.S. Pat. No. 1,921,531 (“the '531 patent”) describes a system for filing pressure cylinders (reference numeral 2) with gas from a vaporizer (reference numeral 1). Although the '531 patent does not implement a compressor to provide gas from the vaporizer to the cylinders, the '531 patent also does not regulate pressure anywhere within the system. For example, the '531 patent does not provide any mechanisms for preventing over-pressure in the system. As another example, the '531 patent does not regulate the dispensing of gas from the vaporizer to the cylinders based on pressure within the vaporizer. As yet another example, the '531 patent does not control evaporation within the vaporizer to regulate pressure and/or the dispensing of gas in the system.